A track ball device is a tool for controlling the movement of the cursor, which includes therein a global object named track ball. A general track ball has a diameter of about 1.5-2.0 cm, which is used in a personal computer for functioning like a traditional mouse device.
As for the video game, the diameter of the track ball generally has a larger diameter to about 10 cm. There are two types of video game track balls, one is a hollow structure and the other is a solid structure.
The solid track ball may not have an appearance of a joint seam, but such a prior solid track ball still encounters a drawback that the entire solid body is made of an Acrylonitrile-Butadiene-Styrene (ABS), which is relatively heavy, not effective in material, and uneasy in operation. While advantages of a hollow track ball are that it is lighter, easy in operation and economical in material.
Previously, a hollow track ball is made by providing two hemispherical sheds and then engaging the two shells by using an ultrasonic wave. But, the respective peripheries of the annular ends of the two shells having a relatively small wad thickness will not exactly align with each other and would accordingly easily result in therebetween a slant joint. As a result, the reject rate of such hollow track ball products as shown in FIG. 1 will be relatively high.